US4881183A - Method and apparatus for emission testing - Google Patents
Method and apparatus for emission testing Download PDFInfo
- Publication number
- US4881183A US4881183A US07/173,419 US17341988A US4881183A US 4881183 A US4881183 A US 4881183A US 17341988 A US17341988 A US 17341988A US 4881183 A US4881183 A US 4881183A
- Authority
- US
- United States
- Prior art keywords
- voltage
- pressure
- analog
- test bench
- emissions
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000013028 emission testing Methods 0.000 title description 4
- 238000000034 method Methods 0.000 title 1
- 238000012360 testing method Methods 0.000 claims abstract description 38
- 230000015654 memory Effects 0.000 claims abstract description 18
- 239000007789 gas Substances 0.000 abstract description 28
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 14
- 239000000523 sample Substances 0.000 description 14
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 7
- 229910002092 carbon dioxide Inorganic materials 0.000 description 7
- 239000001569 carbon dioxide Substances 0.000 description 7
- 229910002091 carbon monoxide Inorganic materials 0.000 description 7
- 229930195733 hydrocarbon Natural products 0.000 description 7
- 150000002430 hydrocarbons Chemical class 0.000 description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 6
- 229910052760 oxygen Inorganic materials 0.000 description 5
- 239000001301 oxygen Substances 0.000 description 5
- 238000005259 measurement Methods 0.000 description 3
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- 230000007175 bidirectional communication Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- 230000000712 assembly Effects 0.000 description 1
- 238000000429 assembly Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/3504—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light for analysing gases, e.g. multi-gas analysis
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/12—Circuits of general importance; Signal processing
- G01N2201/121—Correction signals
- G01N2201/1218—Correction signals for pressure variations
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2201/00—Features of devices classified in G01N21/00
- G01N2201/12—Circuits of general importance; Signal processing
- G01N2201/127—Calibration; base line adjustment; drift compensation
- G01N2201/12746—Calibration values determination
- G01N2201/12753—Calibration values determination and storage
Definitions
- This invention relates generally to automotive emissions testers and particularly to automotive emissions testers that are used with or in computerized engine testing equipment such as that described in the above mentioned related patent applications.
- the recently introduced Modular Computer Analyzer known as the Sun MCA 3000, utilizes an IBM compatible computer in conjunction with a data acquisition system (DAS) that incorporates flagged data and an analog to digital (A/D) RAM that is accessible by both the DAS controller and a system microprocessor.
- DAS data acquisition system
- A/D analog to digital
- a so-called emissions test bench uses infrared light and appropriate optical filters to develop an analog voltage that is indicative of the concentrations of particular gases.
- the particular gases are hydrocarbons (HC), carbon monoxide (CO), and carbon dioxide (CO2).
- An oxygen (O2) concentration measurement may also be obtained, but the apparatus therefor is not part of the present invention.
- Automotive emissions testing while generating extreme interest recently, is not new.
- the particular emissions test bench used with the present invention has also been in use for some time and is not part of the invention.
- the emissions test bench is essentially a spectral photometric gas analyzer that uses a beam of infrared light to determine concentrations of various gases.
- the gases absorb different amounts of light at different wavelengths and the amount of light absorbed at a specific wavelength is related to the concentration, i.e. the number of molecules of the specific gas.
- the bench includes optical filters and sensors.
- the voltage output of the test bench is non-linear and the number of molecules in a sample cell of gas will change depending upon the pressure in the sample cell.
- the prior art IR test bench assembly is equipped with amplifiers to increase its voltage output or span.
- the normal voltage span for such a bench assembly is from 0 to 10 volts.
- the DAS converter has a range of from -10 to +10 volts.
- the emissions test bench assembly output voltage is offset to substantially center it within the range of the A/D converter.
- any gain factor that is present in the bench assembly is measured. Information concerning the calibration pressure, the offset voltage and the gain factor is stored in non-volatile memory and is made accessible to the system microprocessor.
- a principal object of the invention is to provide a novel emissions analyzer.
- Another object of the invention is to provide an emissions analyzer that does not require periodic calibration.
- a further object of the invention is to provide an emissions analyzer that is self compensating for pressure changes.
- FIG. 1 is a partial block diagram of a computer analyzer constructed in accordance with the invention
- FIG. 2 is a partial schematic diagram of the emissions testing portion of FIG. 1;
- FIG. 3 is a series of equations used to correlate voltage and gas concentration.
- a test bench 10 assembly provides a plurality of output voltages to an IR multiplexer (MUX) 12.
- An oxygen sensor 14 and a pressure sensor 16 also supply signals to MUX 12.
- the single output of MUX 12 is coupled to a DAS 20 which includes a DAS multiplexer 22, an A/D converter 24, an A/D RAM 26 and control logic 28.
- DAS 20 operates independently to accept analog signals from MUX 12, or other engine test signals from a source 18, and supply them to A/D converter 24. After conversion to digital form they are loaded into A/D RAM memory 26 under control of control logic 28.
- a bidirectional communications bus 30 interconnects DAS 20 with a system microprocessor 40.
- a CRT display 32 and a printer 34 are operable under control of microprocessor 40 which as mentioned is preferably IBM compatible.
- a keyboard 36 is used to input user commands.
- a bidirectional communication bus 44 couples microprocessor 40 to a system memory 38 which includes a Section 39 of EEPROM.
- Microprocessor 40 also includes an output port 42 that is coupled by a group of control lines 46 to a plurality of solenoids 48 for controlling flow of the various gases and the like. Another group of control lines 50 connects port 42 to MUX 12. The operation of MUX 12 is under control of system microprocessor 40.
- FIG. 2 shows circuit details of test bench assembly 10, shown in dashed lines.
- a power transformer 52 is coupled to an AC line and to a DC rectifier arrangement 54 for developing appropriate DC voltages for application to transistor operated solenoids 56 and 58, that are controlled via control lines 46 from output port 42 of microprocessor 40. It will be appreciated that the various valves controlled by the solenoids are not shown and that the dotted line connecting transistor operated solenoids 56 and 58 indicates that a larger number may be used.
- An emissions test bench 60 is supplied with emissions for analysis by means of a test probe 62 that gathers the automotive exhaust emissions.
- the three output leads from test bench 60 labelled HC, CO and CO2, carry analog voltages representative of the concentrations of HC, CO and CO2 gases in the emission sample.
- the voltages are applied to the non-inverting terminals of operational amplifiers 64, 74 and 84 through zero adjusting circuits 67, 77 and 87 respectively to set the zero output voltages of test bench 60 to correspond to a zero concentration of the respected gases in the emissions sample.
- the inverting terminals of these operational amplifiers are connected to ground through resistors 66, 76, and 86 respectively.
- Three feedback potentiometers 68, 78, and 88 are connected from the outputs to the inverting terminals of operational amplifiers 64, 74, and 84 respectively, and in conjunction with resistors 66, 76 and 86 provide gain adjustments for adjusting the voltage outputs (spans) therefrom.
- the outputs of the operational amplifiers are also supplied to IR MUX 12. Signals on the control leads 50 to MUX 12 are effective to select which of the input voltages appear in the output of the MUX 12, and is therefore supplied to a buffer amplifier 90.
- the output of buffer amplifier 90 feeds the selected voltage to DAS multiplexer 22 in DAS 20.
- the voltage range of the A/D converter 24 (FIG. 1) is greater than the output voltage range or span from test bench 60.
- the test bench zero point is much more likely to drift with temperature change and component tolerances than its span.
- the zero voltage of the test bench may be offset to substantially center it within the range of the A/D converter. This permits the test bench to drift a significant amount and still stay within the range of the A/D converter. Consequently the need for periodic calibration of the tester is obviated and whatever calibration may be required may be accomplished automatically.
- a sample cell is used in conjunction with the IR test bench to analyze and determine the concentrations of the various gases in exhaust emissions.
- the sample cell provides a fixed volume and the IR test bench actually measures the number of molecules of the gas in the sample cell. Pressure changes will affect the number of molecules and the readings, and by measuring the pressure in the sample cell during the exhaust emissions test the errors due to pressure changes can be corrected.
- the equation for determining the number of molecules in the sample cell at the time of calibration of the tester is: ##EQU1## where P is the pressure, N is the number of molecules, T is the temperature, V is the volume of the sample cell and K is a constant. It is readily seen that if the temperature and volume remain constant a change in pressure will result in a change in the number of molecules.
- FIG. 3 shows six polynomial equations that have been derived which relate concentration to voltage, and voltage to concentration, for the different gases HC, CO and CO2. With these polynomial equations, lookup tables are obviated and the computer may perform all calculations.
- a zero reading and a span reading are taken with a known calibration gas (cal gas).
- the zero value for each measured gas (HC, CO and CO2), is stored in non-volatile memory.
- the non-volatile memory may be a conventional memory with a back up battery or it may be a memory of the EEPROM type.
- the span reading measured during calibration is divided by the span reading found from the tables and the gain factor of the test bench is computed. It will be appreciated that a desired span or voltage may be used rather than that found from the tables in order to provide more resolution in the test bench voltage.
- the gain factor for each measured gas is stored in non-volatile memory.
- the calibration pressure is measured and stored in non-volatile memory. When the unit is now turned on and warmed up new zero values are taken and stored in RAM memory. By taking the zero reading, any long term drift of the IR test bench zero is corrected for.
- the analog voltage from the test bench is first corrected for the zero offset. This is performed by subtracting the zero reading taken after the unit is warmed up. Then the voltage is corrected for the gain factor of the test bench. This is accomplished by dividing by the gain factor that was computed during calibration and stored in the non-volatile memory. Then the voltage is corrected for any pressure difference from the pressure measured at calibration. This is accomplished by multiplying the voltage by the ratio of the pressure at calibration and the pressure measured in the sample cell. The equation for this is: ##EQU3## This voltage can now be converted to a gas concentration through use of the lookup tables or use of the polynomial equations.
- the oxygen sensor is not part of the present invention. Suffice it to say that the oxygen sensor has a linear output and consequently does not require a lookup table or polynomial equation. Because of the differences in each oxygen sensor, these readings cannot be compensated for pressure changes.
- potentiometers generally coarse and fine potentiometers
- setting of potentiometers is not critical thus relieving factory personnel (and field personnel) of the need for precise adjustments to calibrate the bench. Should calibration in the field be needed or desired, the user may readily calibrate the unit without needing to adjust the potentiometers.
Abstract
Description
Claims (2)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US07/173,419 US4881183A (en) | 1988-03-25 | 1988-03-25 | Method and apparatus for emission testing |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US07/173,419 US4881183A (en) | 1988-03-25 | 1988-03-25 | Method and apparatus for emission testing |
Publications (1)
Publication Number | Publication Date |
---|---|
US4881183A true US4881183A (en) | 1989-11-14 |
Family
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US07/173,419 Expired - Lifetime US4881183A (en) | 1988-03-25 | 1988-03-25 | Method and apparatus for emission testing |
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Cited By (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1991006852A1 (en) * | 1989-10-26 | 1991-05-16 | Johnson Walter A | Gas purity analyzer and method |
US5046018A (en) * | 1989-09-11 | 1991-09-03 | Nellcor, Inc. | Agent gas analyzer and method of use |
US5179523A (en) * | 1989-10-26 | 1993-01-12 | Johnson Walter A | Method for determining the mole percent of a gas in binary gas mixture |
US5231591A (en) * | 1989-09-11 | 1993-07-27 | Nellcor Incorporated | Agent gas analyzer and method of use |
US5525521A (en) * | 1995-06-15 | 1996-06-11 | Borrego Analytical, Inc. | Cystic fibrosis tester |
US5526280A (en) * | 1994-04-28 | 1996-06-11 | Atwood Industries, Inc. | Method and system for gas detection |
US5636135A (en) * | 1995-09-05 | 1997-06-03 | Ford Motor Company | Method and apparatus for time-alignment of non-plug flow |
GB2343520A (en) * | 1998-11-09 | 2000-05-10 | Raymond Nigel Coupland | Vehicle emissions testing apparatus |
US6321609B1 (en) * | 1998-10-26 | 2001-11-27 | Eai Coporation | Magazine for use with a gas sampling system |
US6701255B2 (en) * | 2000-04-28 | 2004-03-02 | Ppl Electric Utilities Corp. | Emission monitoring system and method |
CN101470073B (en) * | 2007-12-24 | 2011-03-23 | 深圳迈瑞生物医疗电子股份有限公司 | Gas concentration measuring method and apparatus |
WO2011015554A3 (en) * | 2009-08-06 | 2011-04-07 | Robert Bosch Gmbh | Detection device for a test system |
US10154923B2 (en) | 2010-07-15 | 2018-12-18 | Eyenovia, Inc. | Drop generating device |
Citations (14)
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US4093871A (en) * | 1975-10-08 | 1978-06-06 | P.C. Compteurs Limited | Correction circuit |
US4159523A (en) * | 1977-10-07 | 1979-06-26 | Phillips Petroleum Company | Voltage offset network |
US4254469A (en) * | 1979-03-01 | 1981-03-03 | Ncr Corporation | Method and apparatus for offset error correction |
US4314344A (en) * | 1980-01-31 | 1982-02-02 | Dasibi Environmental Corporation | Method and apparatus for generating selected gas concentrations |
US4328546A (en) * | 1980-04-15 | 1982-05-04 | Sun Electric Corporation | Apparatus for evaluating the performance of an internal combustion engine using exhaust gas emission data |
US4348732A (en) * | 1980-01-29 | 1982-09-07 | Sun Electric Corporation | Method and apparatus for engine exhaust analyzer |
US4357668A (en) * | 1980-03-04 | 1982-11-02 | The Perkin-Elmer Corp. | Base line correction method and apparatus |
US4390956A (en) * | 1981-03-06 | 1983-06-28 | The Singer Company | Apparatus for correcting measured gas flow |
US4454853A (en) * | 1981-11-20 | 1984-06-19 | Honda Motor Co., Ltd. | Electronic fuel injection control system for internal combustion engines having exhaust gas recirculation devices |
US4454852A (en) * | 1981-11-19 | 1984-06-19 | Honda Motor Co., Ltd. | Electronic fuel injection control system for internal combustion engines having exhaust gas recirculation control devices |
US4467435A (en) * | 1981-10-05 | 1984-08-21 | Beckman Instruments, Inc. | Infrared gas analyzer having detector elements of differing types |
US4576035A (en) * | 1984-01-05 | 1986-03-18 | Cordis Corporation | Self-calibrating differential condition sensor |
US4638443A (en) * | 1983-02-21 | 1987-01-20 | Hitachi, Ltd. | Gas detecting apparatus |
US4672566A (en) * | 1981-12-01 | 1987-06-09 | Nissan Motor Company, Limited | Device for measuring variable with automatic compensation for offset |
-
1988
- 1988-03-25 US US07/173,419 patent/US4881183A/en not_active Expired - Lifetime
Patent Citations (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4093871A (en) * | 1975-10-08 | 1978-06-06 | P.C. Compteurs Limited | Correction circuit |
US4159523A (en) * | 1977-10-07 | 1979-06-26 | Phillips Petroleum Company | Voltage offset network |
US4254469A (en) * | 1979-03-01 | 1981-03-03 | Ncr Corporation | Method and apparatus for offset error correction |
US4348732A (en) * | 1980-01-29 | 1982-09-07 | Sun Electric Corporation | Method and apparatus for engine exhaust analyzer |
US4314344A (en) * | 1980-01-31 | 1982-02-02 | Dasibi Environmental Corporation | Method and apparatus for generating selected gas concentrations |
US4357668A (en) * | 1980-03-04 | 1982-11-02 | The Perkin-Elmer Corp. | Base line correction method and apparatus |
US4328546A (en) * | 1980-04-15 | 1982-05-04 | Sun Electric Corporation | Apparatus for evaluating the performance of an internal combustion engine using exhaust gas emission data |
US4390956A (en) * | 1981-03-06 | 1983-06-28 | The Singer Company | Apparatus for correcting measured gas flow |
US4467435A (en) * | 1981-10-05 | 1984-08-21 | Beckman Instruments, Inc. | Infrared gas analyzer having detector elements of differing types |
US4454852A (en) * | 1981-11-19 | 1984-06-19 | Honda Motor Co., Ltd. | Electronic fuel injection control system for internal combustion engines having exhaust gas recirculation control devices |
US4454853A (en) * | 1981-11-20 | 1984-06-19 | Honda Motor Co., Ltd. | Electronic fuel injection control system for internal combustion engines having exhaust gas recirculation devices |
US4672566A (en) * | 1981-12-01 | 1987-06-09 | Nissan Motor Company, Limited | Device for measuring variable with automatic compensation for offset |
US4638443A (en) * | 1983-02-21 | 1987-01-20 | Hitachi, Ltd. | Gas detecting apparatus |
US4576035A (en) * | 1984-01-05 | 1986-03-18 | Cordis Corporation | Self-calibrating differential condition sensor |
Cited By (14)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5046018A (en) * | 1989-09-11 | 1991-09-03 | Nellcor, Inc. | Agent gas analyzer and method of use |
US5231591A (en) * | 1989-09-11 | 1993-07-27 | Nellcor Incorporated | Agent gas analyzer and method of use |
WO1991006852A1 (en) * | 1989-10-26 | 1991-05-16 | Johnson Walter A | Gas purity analyzer and method |
US5179523A (en) * | 1989-10-26 | 1993-01-12 | Johnson Walter A | Method for determining the mole percent of a gas in binary gas mixture |
US5526280A (en) * | 1994-04-28 | 1996-06-11 | Atwood Industries, Inc. | Method and system for gas detection |
US5525521A (en) * | 1995-06-15 | 1996-06-11 | Borrego Analytical, Inc. | Cystic fibrosis tester |
US5636135A (en) * | 1995-09-05 | 1997-06-03 | Ford Motor Company | Method and apparatus for time-alignment of non-plug flow |
US6321609B1 (en) * | 1998-10-26 | 2001-11-27 | Eai Coporation | Magazine for use with a gas sampling system |
GB2343520A (en) * | 1998-11-09 | 2000-05-10 | Raymond Nigel Coupland | Vehicle emissions testing apparatus |
GB2343520B (en) * | 1998-11-09 | 2001-08-08 | Raymond Nigel Coupland | Vehicle emmisions testing apparatus |
US6701255B2 (en) * | 2000-04-28 | 2004-03-02 | Ppl Electric Utilities Corp. | Emission monitoring system and method |
CN101470073B (en) * | 2007-12-24 | 2011-03-23 | 深圳迈瑞生物医疗电子股份有限公司 | Gas concentration measuring method and apparatus |
WO2011015554A3 (en) * | 2009-08-06 | 2011-04-07 | Robert Bosch Gmbh | Detection device for a test system |
US10154923B2 (en) | 2010-07-15 | 2018-12-18 | Eyenovia, Inc. | Drop generating device |
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